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264 Chapter 11: Space Warps and Particle Systems
single object, and each particle array can emit a
different type of particle.
Tip: Image motion blur, described in Object
Properties (page 1–117) >MotionBlurgroup,
is known not to work properly with instanced
particles. Use object motion blur with
instanced particles, or use image motion blur
w ith standard particles.
Standard Particles group
When you choose Standard Particles in the Particle
Typesgroup,theoptionsinthisgroupbecome
available. Choose one of the following options to
specify the particle type:
Triangle—Renderseachparticleasatriangle.Use
Triangle particles with noise opacity for steam or
smoke.
Cube—Renders each particle as a cube.
Special—Each particle consists of three intersecting
2D squares. These are effective when you use
aface-mapmaterial,describedinShader B asic
Parameters Rollout (page 2–1466),optionally
along with an opacity map, to create the effect of a
three-dimensional particle.
Facing—Renders each particle as a square that
always faces the v iew. Use with an appropriate
opacity map for bubbles or snowflakes.
Co nstant—Provides a par ticle that remains the
same size, in pixels, specified in the Size spinner.
This size never changes, regardless of its distance
from the camera.
Impor tant: Youmustrendereitheracameraora
perspective view for Constant par t icles to render
correctly.
Tetra—
Renders each particle as a mapped
tetrahedron. Use Tetra particles for raindrops or
sparks.
The default alignment of the tetra particles
depends on t he particle system type and emitter
setup. To specify an alignment, use controls in the
Rotation and Collision rollout (page 2–268).
SixPoint—Renders each particle as a six-pointed,
two-dimensional sta r.
Sphere—Renders each particle as a sphere.
MetaParticle Parameters gro up
When you choose the MetaParticles option in the
ParticleTypesgroup,theoptionsinthisgroup
become available, and metaballs are used as
part icles. Metapart icles take extra t ime to render
but are very effective for spraying and flowing
liquid effect s.
Tens ion—Determines the ti g htness of the p articles,
with regard to their tendency to blend with other
particles. The higher the Tension, the harder the
blobs, and the harder it is for them to merge.
Variation—Specifies the percent of variation of the
Tension e f fec t .
Evaluation Coarseness—Specifies how accurately
themetaparticlesolutioniscalculated. The
higher the coarseness values, the less ca lculation.
However, if the coarseness is too high, there may
be little or no metaparticle effect at all. Conversely,
if the coarsen ess is set too low, the time for
calculation can become extremely long.
Render—Sets the coarseness for metaparticles in
the rendered scene. This option is u navailable
when Automatic Coarseness is on.
Viewport—Sets the coarseness for t he viewport
display. This option is unavailable when Automatic
Coarseness is on.
Automati c Coarseness —A gener al rule is to set the
Coarseness value between 1/4 and 1/2 the size of
the particles. When this item is on, the rendering
coarseness is automatically set, based on the size